Paper feed mechanism for photocopying machine

ABSTRACT

A photocopying machine has copy paper supplied from a continuous roll, and printing is effected while the paper is moving. In order that the paper might be severed while stationary, a variable speed drive is provided which accelerates the paper to form a loop therein, and then stops the paper for severing.

United States Patent Schleifenbaum 1 Feb. 1, 1972 1541 PAPER FEED MECHANISM FOR PHOTOCOPYING MACHINE [56] Relerences Cited (72] Inventor: Karl Schleiienbaum, Haiger. Germany UNITED STATES PATENTS 173] Assignee: Meteor-Siegen Apparatebau Paul Schmeek 3,452,627 7/1969 Goodman et a1 ..83/205 X G.m.b.ll., Haiger, Germany 3,218,918 11/1965 Brindley et al ..35S/28 Filed: May 1969 Primary Examiner-Samuel S. Matthews I21 Appl. No: 824,056 Assistant Examiner--Richard A. Wintercom Attorney-Olson, Trexler, Wolters & Bushnell [30] Foreign Application Priority Data 57] ABSTRACT ()Cl. 24, 1968 Germany ..P 18 02 744.6 A photocopying machine has copy paper suppned from a Com tinuous roll, and printing is effected while the paper is moving. [52] U.S. Cl ..355/29, 83/38, 83/176, In Order that ha paper might be Severed while Stationary, a 83/24, 101/224 variable speed drive is provided which accelerates the paper [51 1 Int. Cl. t t 1 t l 1 l i ..G03b 27/48 to form a leap therein and the stops the paper f severing [58] Field ol'Search ..355/28,29;B3/38,176,241;

21 Claims, 5 Drawing Figures mammm 1m? 3.839.055

SHEET 4 OF 4 Inner?!- jdzrl 665123272 baam/ PAPER FEED MECHANISM FOR PI-IOTOCOPYING MACHINE This invention relates to the severing of a sheet of material which is continuously transported at its leading end. To enable the severing to be effected, a loop of material is formed after the severing station in the feed direction and the sheet is severed from the web of material when the end of the sheet is stationary, while the sheet material stored in loop is transported onwards continuously. The invention relates more particularly but not exclusively to the severing of a copying sheet from a storage roll thereof in the length required for copying a master sheet, both the beginning and the end of the master sheet being sensed and the feed of copying sheet material to the copying station and severance of the copying sheet being controlled in dependence thereon, and to a device for carrying out this process.

It is known to start the feed of the copying material drawn off a storage roll in dependence on the front edge of the master sheet being introduced into a photocopying machine, that edge being for example sensed by means of a light-sensitive device or a microswitch. In this connection, the method of control is to bring the front edge of the master sheet and the front edge of the copying sheet together, and then to transport the two together into the copying station for exposure and developing.

The considerable length of master sheets and copying sheets in photocopying machines results in the leading end of the sheet being disposed in the exposure device, or having passed it, before the trailing end of the master sheet has reached the sensing device controlling the cutter for severing the copying sheet from the storage roll in the length finally required. It is therefore impossible completely to halt the transport of master sheets and copying sheets while severing is in progress; this can only be done when the leading end of the master sheet moves into the copying station after severing of the copying sheet.

It has therefore been necessary to allow for the fact, when the cutters are triggered by the trailing end of the master Sheet, when the copying sheet is severed while it was being fed, a clean edge could not be obtained, and in particular it was impossible to carry out the severing cut-for example by means of moving knives-so precisely that the copying sheet did not require any subsequent trimming.

In order to make it possible to carry out the severing cut with the copying material stationary, and thus more accurately, in spite ofthe copy job running onwards, it has also already been proposed to feed the master and copy sheets at a speed continuously higher than that of the transporting mechanisms further downstream, thus forming loops in the sheets, and to terminate the feed of copying material and cut off the copying sheet as soon as the end of the master sheet was sensed. However, this forms a loop of continually increasing size, amounting to the whole length of the master sheet, so that this process cannot be used when there are fairly large differences in the length of the sheet to be severed.

One aspect of the present invention resides in a method of severing a sheet of material while the leading portion is moving continuously, in which the material to the rear of the leading portion is first accelerated relative to the leading portion to form a loop of predetermined length and is then reduced to zero, and the stationary material is severed while the loop is exhausted by the continued movement ofthe leading portion.

When the method according to the invention is applied to the operation described at the beginning of severing a copying sheet from a storage roll thereof in the length required for copying a master sheet the feed of copying sheet material is accelerated while the continuous copying operation is in progress and then brought completely to a standstill in the re gion of an end portion of the master sheet in order to form a loop of copying sheet corresponding in length to the remaining end portion of the master sheet between the storage roll and the copying station. Thus only the end portion of the coping sheet is measured off in accelerated fashion-as soon as its final length is indicated in consequence of the end of the master sheet being sensed or otherwise, for example in order to attain a definite length-and the ascertained end of the copying sheet is held fast in the correct location relative to the cutter, so that the copying sheet can be severed with the greatest precision from the stationary strip of copying material. There is nevertheless no hindrance to the copy job running uniformly through the copying station.

A loop of equal dimensions is preferably formed regardless of different feed speeds. In the case of photocopying machines. the feed speed depends above all on the density and contrast of the master sheet, so that the copying material is correctly exposed with constant brightness on the part of the exposure lamp. The fact of the feed speed having to be regulated in the large ratio ofabout l:200 resulted in the copy job being attended with considerable difiiculties in the case of all previously known severing processes. These difficulties are avoided by the formation of a loop which is always of the same length.

A second aspect of the invention resides in apparatus for severing a copying sheet from a storage roll differing mounting means for at least one storage roll of copying material, a first set oftransport rollers arranged to draw copying material from the roll and to convey it past a cutter to a continuously driven second set of transport rollers, a variable speed gear drive for the first set of transport rollers arranged first to increase their speed with respect to the second set for a prescribed number of revolutions of the rollers of the second set and then to reduce the speed of the first set to zero, and means for operat ing the cutter to sever the material while the speed of the first set is zero.

The apparatus according to the invention is preferably equipped with a plurality of storage rolls of copying material of differing width and/or differing quality, and there is a plurality of pairs of transport rollers, capable of selective engagement, which feed the copying material on the associated storage roll to a common cutter and to common second and third pairs of transport rollers. Provided that there are storage rolls with copying material of differing width, the individual storage rolls are engaged in dependence on sensing members, such as photosensitive devices, microswitches or the like, which detect the width of the master sheet as it is being introduced and select the storage roll with copying material of the same width.

The invention will be more readily understood by way of example from the following description of a photocopying machine in accordance therewith, reference being made to the accompanying drawings, in which FIG. 1 is a vertical sectional view of part of the copying machine,

FIG. 2 is a cross section along the line IIII in FIG. 3 through the gearbox ofthe machine of FIG. 1,

FIG. 3 shows an elevation of the arrangement illustrated in FIG. 2 in the direction of the arrow A,

FIG. 4 is a section on the line lV-IV in FIG. 2, and

FIG. Sis a section along the line V-V in FIG. 3.

The photocopying machine has a table plate in the form of a track I over which the master sheets (transparent originals) to be copied are introduced. Below the table plate, a housing 2 is secured to the frame 3 of the machine. The lateral walls of the housing 2 carry mountings, which are not illustrated in detail, for three storage rolls 4, 5 and 6 of copying paper. From each ofthe storage rolls, which can rotate in their mountings, copying paper runs off via tensioning rollers 7 and guide rollers 8.

Copying paper is fed from the rolls 4, 5 6 by first sets of transparent rollers, the pair of transport rollers 9 being provided for the storage roll 4, the pair of transport rollers 10 for the storage roll 5, and the pairs of transport rollers II and 12 for the storage roll 6. These first sets of transport rollers convey the copying paper through converging paper guides 13, 14 and 15 respectively to a cutter comprising a cutting table 16 and a knife 17, which acts in conjunction with the edge 18 of the cutting table 16. The sets 9 or 10 or 11 and 12 of transport roller may be selectively coupled to the drive of a gear box 42 which will be described in detail later, of the photocopying machine, selection being carried out in dependence on the setting of a selector switch of which the setting knob 19 is shown above the track I or, if the storage rolls 46 are of paper of differing widths, in dependence on sensing members such as photosensitive cells, microswitches or the like, which sense the width of the master sheet introduced via the introductory track 1.

The copying paper from the selected roll 4, 5, 6 and pushed by the appropriate first set of transport rollers past the cutting l6, I7 is passed to a second pair oftransport rollers 22 located at the start of a paper guide 23; after the paper leaves the cutter 16, 17 it passes between a pair of transport rollers driven synchronously with the first sets oftransport rollers and then over a paper guide table 21, At the end of the paper guide 23, the paper passes between the rollers of a pair oftransport rollers 24, where it meets the master sheet. From the nip 25 of the rollers 24 onwards, the Copying pair consisting of the master sheet and the copying sheet is guided with the aid of transport belts 26 past the exposure drum 27 which is illustrated only in diagrammatic fashion,

The master sheet pushed over the guide track 1 is picked up by the pair of transport rollers 28, conveyed through the paper guide 29 to the pair oftransport rollers 30 and introduced into the paper guide 3|. As the front edge of the master sheet passes into the line of action 32 ofa photosensitive device 33, the latter delivers a pulse to a clutch which couples the selected first set oftransport rollers 9, or 10, or I I and 12, to a continuous chain drive 121: (FIG. 2 where only the clutch 12a of the pair of transport rollers 12 is illustrated I, and as described above starts to feed the relevant copying paper past the cutter as far as the pair of transport rollers 24, where the copying paper meets the master sheet guided by the paper guide 31 and the further pair of transport rollers 34 FIGv I), The master sheet is conveyed by the pairs of transport rollers 28, 30 and 34, and the selected copying material is conveyed front the selected storage roll at the same feed speed, and this continues unaltered as long as the master sheet remains in the line of action 35 of a second photosensitive device 36 which is arranged upstream of the device 33. However, as soon as the trailing edge of the master sheet leaves the line of action 35 of the device 36, the latter delivers an electrical pulse which trips the control for the first set of transport rollers of the selected storage roll and ofthe cutter I6, 17.

Each set of transport rollers 9, l0 and 11 is driven by a clutch similar to the clutch 12a of FIG. 2, all the clutches being driven by the common chain drive 12c. Chain drive 121? is driven by a chain drive through a sprocket 39, spur gear 3% fast with sprocket 39 and a meshing gear 12d fast with sprocket wheel 12b with which chain drive 12c meshes. In addition to sprocket 39 chain drive 40 has sprocket 37 on the shaft 41 of gearbox 42 and sprocket 38 which drives the pair of rollers 20 through spur gear 38a fast with sprocket 38 and spur gear 200 (FIG. 3) fast with one roller 20. The gearbox 42 is driven front the main speed regulated drive, not shown, via the belt pulley 43, a V beIt 44 and a belt pulley 45 disposed on the input shaft 46 of the gearbox 42. The main drive, driving both the gearbox 42 and the exposure drum 2? is regulated in speed according to the density ofthe master copy.

In normal operation, when the selected set 9, 10, or 11 and 12 and the other pairs of transport rollers for the copying material are being driven synchronously, so that the copying material is being fed at the same speed as the master sheet being introduced, the chain drive 40 is driven via the spur gear 460 disposed on the shaft 46, an intermediate gear 47, the spur gear 48 meshing with the latter, and the differential gear train consisting of the driving gear 49, the planetary pinions 50 and the takeoffgear 51, since the spur gear 48 is fast with the driving gear 49, and the takeoff gear 51 is formed with the hollow takeoff shaft which carries the sprocket 37 of the chain drive 40. i

In this initial condition, the central spindle 41 of the differential gear is at rest, and the pinions 50 rotate about a pin 52 which is mounted on and extends perpendicularly with respect to the spindle 41v The driving and takeoffgears 49, SI of the differential gear train accordingly run at the same speed in opposite senses,

A pulse from the photosensitive device 36, signalling the ar' rival of the trailing edge of the master sheet, causes energizetion ofa magnetic clutch 53 at the free end of the input shaft 46 of the gearbox 42. The excited clutch 53 links the shaft 46 with a cam disc 58 via the spur gear 54, an intermediate stage consisting of the spur gears 55 and 56 and serving to reduce the torque at the magnetic clutch, and a spur gear 57, The link continues for one revolution of the cam disc 58, and is then interrupted again by deenergization ofthe clutch 53.

The design and function ofthe cam disc 58 may best be seen in FIG. 4. A groovelike cam track 59, is milled into the surface of one side of the cam disc 58 and has three sectors 60, 61, 62 each subtending at the axis of shaft 46. The cam follower rollers 63 and 64 engage in the cam track being spaced at 120 so that when the cam disc 58 is in its inoperative position (as illustrated in FIG. 4) they are located at opposite ends of the first sector 60 ofthe cam track; when the cam disc 58 rotates, the said rollers run in the cam track 59.

The first sector 60 of the cam track 59 extends concentrically with the axis ofthe shaft 46 ofthe gear 42, on which shaft the cam disc is disposed. The sector 61 of the cam track 59, which follows in the direction opposite to the direction (indicated by the arrow 65 in FIG. 4) in which the cam disc 58 rotates, becomes rate remote from the axis of the shaft 46 in such a manner that when the cam disc 58 rotates in direction 65 the roller 63 pivots at increasing speedi.e., is accelerated-about the spindle 41 in the gear 42. The roller 63 is in fact rotatably mounted on the end of a lever 66 which is keyed at the other end to the spindle 41 (FIG. 2). In FIG. 4, the lever 66 and the spindle 41 are merely indicated schematically.

When the end ofthe sector 61 of the cam track has reached the roller 63 as the cam disc 58 is rotated away from the in operative position shown in FIG. 4, i.e., when the cam disc has rotated through 120, the roller 63 has been pivoted through 0 about the axis of spindle 41, as shown in dashed line in FIG, 4. This correspondingly pivots the spindle 41 together with the pin 52 of the pinion 50 with accelerating motion, with the result that the speed of the takeoff gear 51 and thus of the sprocket 37 is increased progressively from their initial constant value. This speed is also transmitted to the first set of transport rollers of the selected storage roll 4, 5, 6 of copying paper, and to the third pair of transport rollers 20. Because the second pair of transport rollers 22 continued on the contrary to run at the same speed, being driven independently of gearbox 42, the higher feed speed of the first set and third pair of transport rollers causes a loop of copying paper to pile up above the guide table 21 between the third pair of transport rollers 20 and the second pair of transport rollers 22.

During the same period, the first sector 60 of the cam track 59 is moved past the roller 64. The roller 64 is likewise disposed on a pivoting lever 67 which may be seen in FIGS. 3 and S which is on shaft 68 (FIG. 5). Shaft 68 carries a crank 670 on which is pivotally carried a pushrod 67b (FIG. 3) actuating the knife 17 ofthe cutter via bell crank levers (FIG. 3). However, since the sector 60 ofthe cam track 59 extends concentrically with the rotational axis of the cam disc 58, the roller 64 is not pivoted about the axis of shaft 68 during the first 120 movement ofthe cam disc.

Ifthe cam disc 58 now rotates further, and the roller 63 runs through the third sector 62 of the cam track 59, the lever 66 ivots back again because the cam track 59, which became more remote from the axis of the shaft 46 in the portion 61, now approaches this axis again. As a consequence, the pin 52 of the pinion 50 is also pivoted back, and instead of the superimposed rotations being added (the drive via the driving gear 49, and the pivoting of the pinion 50), subtraction now takes place. The third sector 60 of the cam track 59 is so designed that the circumferential speed of the pinion 50 is just equal and opposite to the circumferential speed of the driving wheel 49, so that the resultant speed at the takeoff gear 51 is zero, and the chain drive 40 remains stationary. This also stops the selected first set of transport rollers and the third pair of transport rollers 20, and the strip of copying paper material remains at rest as far as the third pair of transport rollers 20. However, the second pair of transport rollers 22 being still driven, continue to convey the copying paper and exhausts the loop which has previously been piled up between the pairs of rollers 20, 22.

While the roller 63, which controls the differential gear, is moving through the sector 62 of the cam track 59, the roller 64, which controls the cutter, is rolling in the portion 61 ofthe cam track 59. The lever 67 thus pivots with increasing speed through 90 into the position shown in dashed line in FIG. 5, and moves the knife 17 at correspondingly increasing speed past the cutting edge 18 of the table I6 upon which the copying paper at that time stationary, with the result that the copying sheet is severed from the storage roll.

The cam disc 58 has by now carried out two thirds of its revolution. On the remaining third, the roller 63 of the differential gear moves in the neutral sector 60 of the cam track 59, so that the pinions 50 of the differential gear in the gearbox 42 remain in the inoperative position illustrated in FIG. 2. At this instant however, the clutch (for example 12a) which linked the selected first set of transport rollers to the chain drive 120 has already opened again, so that renewed movement of the chain drives 40 and [2c has no further effect on the selected set of transport rollers 9, or 10, or II and 12. On the contrary, the copying paper on the selected roll 4, 5 or 6 remains in the inoperative position which is assumed after the cam disc had carried out two thirds of a revolution. However, the spindle 38 and thus the pair of transport rollers continue to be driven at the synchronous speed, so that the sheet severed from the leading end of the paper web is fed away from the cutter. At the same time, the roller 64 moves in the third sector 62 of the cam track, so that the lever 68 pivots back and the knife 17 opens again ready for the next operation.

The distance of the cutter l6, 17 from the rollers 24 is so chosen in relation to the distance of the photosensitive device 36 from those rollers 24 that, when the cutter is operated to sever the copy paper in the second third of the revolution of the cam disc 58, i.e., at a fixed time interval after the trailing edge of the master sheet passes the device 36, the length of severed copying paper remaining upstream of rollers 24 is equal to the length of the master sheet still to pass through those rollers 24, Therefore, regardless of the overall length of the master sheet, the copy sheet is always severed at the position to give a corresponding severed length.

As the cam disc is driven at a constant speed determined by the speed of the exposure drum 27, the period for which, and the manner is which, the copy paper is accelerated by the rollers 20 and the first set 9, or 10, or 11 and 12 in uniform from master sheet to master sheet and a loop of uniform dimensions is accumulated between rollers 20, 22 each time.

The speed of drum 27 may of course vary from master sheet to master sheet, dependent on the density ofthe material to be copied. As however the speed ofthe cam disc 58 is controlled by the speed of the drum 27, the dimensions of the loop formed between rollers 20, 22 is constant regardless of the speed of the leading end of copying sheet.

FIG. 4 reveals that the last part of the second sector 61 of the cam track-shortly before the cam track 59 merges into its third sector 62does not become any more remote from the shaft 46, so that no further movement is imparted to the rollers 63 and 64 in that partial region of the portion 6! of the cam track. In this way, the accelerated movements both in loop formation and in the severing operation are stopped without the occurrence of any detrimental slip in the paper feed or any dangerous abrupt retardation ofthe knife.

The same purpose, namely the prevention of slip between the transport rollers and paper and the production of large inertia forces, is also served by designing the main part of the second sector M of the cam track in such a manner that the transport rollers driven by the gearbox and the knife I? of the cutter are driven in accelerated fashion, so that there is a gradual increase in speed.

Since the third sector 62 of the cam track must necessarily impart uniform speed to the roller 63 so that the chain drives 40 and 12c are brought to a complete standstill, the shape of sector 62 of the cam track cannot be chosen in relation to the inertial forces of the knife 17, which is caused to close when the associated roller 64 is running through the sector 62 of the cam track. For this reason, as shown particularly in FIG. 3, the arrangement has been made such that the roller 64 actuates the knife 17 via the crank 67:: and pushrod 67b, which are at an angle of about 90 to one another when the knife 17 is in its open position, and of about 0 to one another when the knife is in its closed position. In this way, the movement of the pushrod 67b, which proceeds in accordance with a sinusoidal function, becomes superimposed on the pivoting movement of the roller: as the roller 64 is moved in the second sector 61 of the cam track first of all at low speed and then at progressively increasing speed, the pushrod 67b first ofall follows this pivoting movement at practically uniform speed, but as the roller 64 ends its pivoting movement the transmission factor decreases in accordance with a sinusoidal function defined by the sector 61 of the cam track. As the roller 64 is then pivoted back at uniform speed by the sector 62 of the cam track, the knife 17 none the less moves back into its initial position, first of all at low speed, but increasing in accordance with the same sinusoidal function only in the reverse sense.

At the end of one full revolution of the cam disc, a locking pawl 69 (FIG. 4) which is urged by a spring 70 against the circumferential surface of the cam disc 58, latches in a cutaway 71 at the circumference of the cam disc 58. The lever 69a which carries the locking pawl 69 at its end extends substantially tangentially to the circumference of the cam disc 58, and is pivotally mounted about a pin 74 on an arm 75. In its turn, the arm 75 is capable of pivoting about the shaft 46, and bears by way of its free end against a damping member 76 which allows the arm 75 to carry out only small pivoting movements.

If the locking pawl 69 latches into the cutaway 7l under the action of the spring 70 as the cam disc 58 ends a revolution in the direction of the arrow 65 (FIG. 4], the cam disc 58 carries the arm 75 with if for a short distance against the force of the member 76, this action taking place due to the inertia of the cam disc and via the lever 60a. However, the spring force stored in the element 76 then allows the arm 75 to pivot back, and thus returns the cam disc 58 to its inoperative position, which it had previously slightly overrun.

A further lever 81 is mounted on the arm 75, being similarly pivotable at the end about the pin 74, and engages by way of a guide peg 80 at the other end in a circular track 73 laterally milled into the spur wheel 55 of the intermediate stage driving the cam disc 58. A spring 82 biases the lever 81 in the direction of the rotational axis of the spur wheel 55. A peg 83 on the lever 81 engages in an elongated hole in the lever 69a, without however affecting the pivotability of the lever 69a as long as the peg 80 is disposed in the circular track 73.

However, a further rectilinear, guide track 77 provides a short circuit connection" extending in the shape of a chord in relation to the associated portion of the circular track 73 between two points on that circular track, and if the guide peg 80 enters this guide track 77 because the spring 82 is biassing it in this direction, the lever 8! acts via the peg 83 and the lever 69a to lift the locking pawl 69 out of its locking position in the cutaway 71. When the peg 80 is proceeding normally in the circular track 73, which, when the cam disc 58 is being driven, rotates in the direction of the arrow 72 and thus in the opposite direction to the cam disc (arrow 65), the guide peg 80 is prevented from entering the guide track 77 by a tongueshaped deflector 79, which in the illustration of FIG. 4 is spring-loaded to rotate anticlockwise. If the peg 80 runs over the fork to the guide track 77 in the direction ofthe arrow 72 upon rotation of the spur wheel 55 and thus of the circular track 73 [because of the transmission ratio the spur wheel 55 rotates twice as fast as the cam disc 58, i.e., to one revolution of the cam disc there are two revolutions of the spur wheel 55), that peg forces the deflector 79 to the side and thus blocks the path to the guide track 77; this condition is illustrated in FIG. 4. The guide peg 80 is also in this position at the instant at which the locking pawl 69 latches into the cutaway 71 at the end ofa revolution of the cam disc 58. However, the fact that the arm 75, which carries all the levers, is sprung as described above causes the guide peg 80 to overrun the deflector 79, which thereupon pivots anticlockwise, and steers the guide peg 80 into the guide track 77 when the cam disc 58 and the spur wheel 55 move back in the opposite direction to the arrows 65 and 72 respectively. Because the force of the spring 82 is stronger than the force of the spring 70, the lever 81 then lifts the locking pawl 69 out ofits locking position.

However, the cam disc 58 is meanwhile disposed in its inoperative position. Any tendency on the part of the cam disc 58 to depart from this inoperative position is prevented by the fact that the guide peg 80 comes to rest in a safety notch 78 in the guide track 77 When the next cycle of the cam disc 58 starts, the guide peg 80 first ofall proceeds in the guide track 77, and then passes into the circular track 73 again. The cutaway 7t in the locking awl 58 has meanwhile been moved past the locking pawl 69, so that the latter is then pulled by the spring 70 against the face of the cam disc 58, and slides along the same until it again latches into the cutaway 71 as the cam disc finishes rotating, and stops the cam disc.

What is claimed is:

l. A method of severing a sheet of material from a continuous web, in which the leading portion ofthe material to be cut off is moved continuously during the severing action, the material to the rear of the leading portion is first accelerated relative to the leading portion to form a loop of predetermined length and is then decelerated to rest, and the stationary material is severed upstream of the loop, the loop being ex boosted by the continued movement ofthe leading portion.

2, A method according to claim I for severing a copying sheet from a storage roll thereof in the length required for copying a master sheet, in which. while the continuous copying operation is in progress, with continuous movement of the copying sheet, the feed of the copying sheet is first accelerated in order to form a loop of copying sheet corresponding in length to the remaining end portion of the master sheet between the storage roll and the copying station, and is then brought to a standstill and the stationary part of the copying sheet is severed.

3. a method according to claim I in which a loop of the same length is formed regardless ofdifferent feed speeds.

4. A method according to claim 2 in which a loop of the same length is formed regardless ofditTerent feed speeds.

5. Apparatus for severing a copying sheet from a storage roll comprising mounting means for at least one storage roll of copying material, a first set of transport rollers arranged to draw copying material from the roll and to convey it past a cutter to a continuously driven second set of transport rollers, a variable speed gear drive for the first set of transport rollers arranged first to increase their speed with respect to the second set for a prescribed number of revolutions of the rollers of the second set and then reduce the speed of the first set to zero, and means for operating the cutter to sever the material while the speed ofthe first set is zero.

6. Apparatus according to claim 5, in which a third set of transport rollers is arranged after the cutter in the direction in which the copying material is fed and driven in synchronism with the first set of transport rollers, the loop of copying material being formed between the third and second sets of transport rollers.

7. Apparatus according to claim 5, in which the variable speed gear drive comprises a differential gear, the cage of which is stationary when the first and second sets oftransport rollers are driven synchronously, and means for turning the cage in one direction in order to impart a higher speed to the first set of transport rollers. and in the opposite direction in order to bring the said first set to a standstill.

8. Apparatus according to claim 7, in which the means for turning the cage comprises a cam disc arranged to be coupled to the drive for the transport rollers in order to control the rotation of the cage.

9. Apparatus according to claim 8, in which a cam track is formed in the surface ofa side of the cam disc and a cam follower, which is arranged on the free end of a lever connected with the cage runs in the cam track.

10 Apparatus according to claim 9, in which the cam track has a second cam follower arranged to control the cutting movement ofthe cutter.

ll. Apparatus according to claim 10, in which the cam track has three sectors, preferably each subtending l20 and the two cam followers engage in the cam track at a spacing of one sector.

12. Apparatus according to claim [1, in which the first sector, which is disposed between the rollers in the inoperative condition, and in which the second cam follower runs when the cam disc first rotates, extends concentrically with the rota tional axis of the cam disc.

13. Apparatus according to claim H, in which the second sector of the cam track in the direction opposite to the direction of rotation of the cam disc, in which sector the first cam follower runs when the cam follower first rotates, is arranged to impart accelerated movement to both the cage, while the loop of copying sheet is being formed, and to the cutter during the severing operation.

14. Apparatus according to claim II, for which the third sector of the cam track is arranged to rotate the cage at a speed and in a direction such that the output shaft of the differential gear is brought to zero speed 15. Apparatus according to claim [0, in which the second cam follower is arranged to actuate the knife via a crank and a pushrod which are at an angle of about to one another when the knife is in its open position, and at an angle of about 0 to one another when the knife is in its closed position.

l6. Apparatus according to claim 9, in which means for sensing the end of the master sheet actuates a clutch for the cam disc.

17. Apparatus according to claim 9, in which a locking pawl is provided to stop the cam disc in its inoperative position.

18. Apparatus according to claim [7, in which the locking pawl which is biased in the locking direction and slides on the circumferential edge of the cam disc when the latter is rotating, is disposed on an arm sprung in the circumferential direction ofthe cam disc, so that at the end ofa working cycle the cam disc rotates somewhat beyond its inoperative position against the spring force of the arm, and when return movement into the inoperative position occurs under the action of the spring force a lever controlled by the spring force releases the locking pawl.

19. Apparatus according to claim 18, in which a guide peg fastened to the lever proceeds in a circular track driven together with the cam disc and in that in the region of the portion of the circular track corresponding to the inoperative position of the cam disc there is a straight guide track linking two points on the circular track in the form of a chord, which straight guide track is closed to the guide peg by a deflector when the circular track rotates in the forward running direction of the cam disc, but the said deflector allows the guide peg to enter the guide track under the force of a spring acting on the lever when the cam disc moves back, with the result that the lever releases the locking pawl.

20. Apparatus according to claim 19, Ill which the guide track has a safety notch in which the guide peg engages when the cam disc is not being driven and is disposed in its inopera tlve position.

2|. Apparatus according to claim 5, in which there is a plurality of storage rolls of copying material of differing width and/0r differing quality, and in which each storage roll has a 

1. A method of severing a sheet of material from a continuous web, in which the leading portion of the material to be cut off is moved continuously during the severing action, the material to the rear of the leading portion is first accelerated relative to the leading portion to form a loop of predetermined length and is then decelerated to rest, and the stationary material is severed upstream of the loop, the loop being exhausted by the continued movement of the leading portion.
 2. A method according to claim 1 for severing a copying sheet from a storage roll thereof in the length required for copying a master sheet, in which, while the continuous copying operation is in progress, with continuous movement of the copying sheet, the feed of the copying sheet is first accelerated in order to form a loop of copying sheet corresponding in length to the remaining end portion of the master sheet between the storage roll and the copying station, and is then brought to a standstill and the stationary part of the copying sheet is severed.
 3. a method according to claim 1 in which a loop of the same length is formed regardless of different feed speeds.
 4. A method according to claim 2 in which a loop of the same length is formed regardless of different feed speeds.
 5. Apparatus for severing a copying sheet from a storage roll comprising mounting means for at least one storage roll of copying material, a first set of transport rollers arranged to draw copying material from the roll and to convey it past a cutter to a continuously driven second set of transport rollers, a variable speed gear drive for the first set of transport rollers arranged first to increase their speed with respect to the second set for a prescribed number of revolutions of the rollers of the second set and then reduce the speed of the first set to zero, and means for operating the cutter to sever the material while the speed of the first set is zero.
 6. Apparatus according to claim 5, in which a third set of transport rollers is arranged after the cutter in the direction in which the copying material is fed and driven in synchronism with the first set of transport rollers, the loop of copying material being formed between the third and second sets of transport rollers.
 7. Apparatus according to claim 5, in which the variable speed gear drive comprises a differential gear, the cage of which is stationary when the first and second sets of transport rollers are driven synchronously, and means for turning the cage in one direction in order to impart a higher speed to the first set of transport rollers, and in the opposite direction in order to bring the said first set to a standstill.
 8. Apparatus according to claim 7, in which the means for turning the cage comprises a cam disc arranged to be coupled to the drive for the transport rollers in order to control the rotation of the cage.
 9. Apparatus according to claim 8, in which a cam track is formed in tHe surface of a side of the cam disc and a cam follower, which is arranged on the free end of a lever connected with the cage runs in the cam track.
 10. Apparatus according to claim 9, in which the cam track has a second cam follower arranged to control the cutting movement of the cutter.
 11. Apparatus according to claim 10, in which the cam track has three sectors, preferably each subtending 120* and the two cam followers engage in the cam track at a spacing of one sector.
 12. Apparatus according to claim 11, in which the first sector, which is disposed between the rollers in the inoperative condition, and in which the second cam follower runs when the cam disc first rotates, extends concentrically with the rotational axis of the cam disc.
 13. Apparatus according to claim 11, in which the second sector of the cam track in the direction opposite to the direction of rotation of the cam disc, in which sector the first cam follower runs when the cam follower first rotates, is arranged to impart accelerated movement to both the cage, while the loop of copying sheet is being formed, and to the cutter during the severing operation.
 14. Apparatus according to claim 11, for which the third sector of the cam track is arranged to rotate the cage at a speed and in a direction such that the output shaft of the differential gear is brought to zero speed.
 15. Apparatus according to claim 10, in which the second cam follower is arranged to actuate the knife via a crank and a pushrod which are at an angle of about 90* to one another when the knife is in its open position, and at an angle of about 0* to one another when the knife is in its closed position.
 16. Apparatus according to claim 9, in which means for sensing the end of the master sheet actuates a clutch for the cam disc.
 17. Apparatus according to claim 9, in which a locking pawl is provided to stop the cam disc in its inoperative position.
 18. Apparatus according to claim 17, in which the locking pawl which is biased in the locking direction and slides on the circumferential edge of the cam disc when the latter is rotating, is disposed on an arm sprung in the circumferential direction of the cam disc, so that at the end of a working cycle the cam disc rotates somewhat beyond its inoperative position against the spring force of the arm, and when return movement into the inoperative position occurs under the action of the spring force a lever controlled by the spring force releases the locking pawl.
 19. Apparatus according to claim 18, in which a guide peg fastened to the lever proceeds in a circular track driven together with the cam disc and in that in the region of the portion of the circular track corresponding to the inoperative position of the cam disc there is a straight guide track linking two points on the circular track in the form of a chord, which straight guide track is closed to the guide peg by a deflector when the circular track rotates in the forward running direction of the cam disc, but the said deflector allows the guide peg to enter the guide track under the force of a spring acting on the lever when the cam disc moves back, with the result that the lever releases the locking pawl.
 20. Apparatus according to claim 19, in which the guide track has a safety notch in which the guide peg engages when the cam disc is not being driven and is disposed in its inoperative position.
 21. Apparatus according to claim 5, in which there is a plurality of storage rolls of copying material of differing width and/or differing quality, and in which each storage roll has a first set of transport rollers capable of selective engagement, which feed the copying material on the associated storage roll to a common cutter and to common third and second sets of transport rollers. 